1. Field of the Invention
The present invention relates to an optical module apparatus for optically coupling optical elements to each other with a low loss, or more in particular to an optical module apparatus for holding an optically coupled state using a plurality of wedges, a method of fabricating the optical module apparatus and a projection television using the same.
2. Description of Related Art
In mounting by integrating optical elements such as a semiconductor laser, an optical waveguide and an optical fiber as an optical module, it is indispensable that the optical elements be optically coupled with each other in stable fashion with a low loss. Mounting methods for optically coupling optical elements roughly include an active alignment and a passive alignment.
When a semiconductor laser and an optical waveguide are optically coupled to each other, for example, the active alignment method is basically used in such a manner that a semiconductor laser is generated, the light beam emitted from the semiconductor laser is coupled to the optical waveguide, and the output light power from the optical waveguide is monitored while searching for an optimum position and fixing the semiconductor laser and the optical waveguide at the particular position.
The passive alignment method, on the other hand, includes a method in which at least a fitting protrusion and a fitting recess are formed beforehand at a predetermined position on each of the board carrying the semiconductor laser and the holding member of the optical waveguide so that the optical coupling is established by fitting the protrusion and the recess to each other with a mechanical accuracy alone, and a method in which the semiconductor laser and the optical waveguide are fixed at the desired position utilizing the self-aligning effect of the molten solder in mounting the semiconductor laser and the optical waveguide on a board.
Generally, the active alignment method requires a three-dimensional positioning process to attain an optimum position. Since this positioning process leads to a high cost, most parts of the mounting process desirably remain unadjusted as in the passive alignment method.
Depending on the type and the configuration of the optical elements to be coupled, however, the passive alignment method may be difficult to implement. For example, consider the method disclosed in Japanese Patent No. 3059171. In this method, the output light of a W-class semiconductor laser, which is composed of an active layer about several hundred μm wide and about several μm thick and thus having extremely asymmetric horizontal and vertical sizes, is intended to be optically coupled with high efficiency to an optical fiber having a core diameter of several tens of μm. According to this method, the optical coupling is realized in such a manner that an optical waveguide formed of a soft material such as silicone resin is placed directly butted against a light exit end surface of the semiconductor laser and an optical connecting end surface of the optical fiber. This method, in which the optical waveguide is formed of a soft material, makes it possible to bring the end surfaces of the semiconductor laser and the optical waveguide into direct contact with each other without damaging the light exit end surface of the semiconductor laser, thereby realizing the optical coupling with a low loss. Nevertheless, the fact that the optical waveguide is formed of a soft material unavoidably causes variations of the outer size of the optical waveguide ranging from several μm to a maximum of several tens of μm. Actually, therefore, the passive alignment method described above is very difficult to employ in mounting an optical module. Even in the active alignment method, the semiconductor laser and the optical waveguide cannot be easily fixed in stable fashion at an optimum position after adjustment.
Specifically, according to the prior art, the outer dimensions of the optical waveguide fabricated of a soft resin material such as silicon are difficult to control with high accuracy. In the passive alignment method including means for self alignment using the molten solder or fitting between protrusions and recesses, the optical waveguide cannot be easily connected optically with the optical element such as a semiconductor laser or an optical fiber with low loss. In the active alignment method, on the other hand, an optical module cannot be easily fixed in stable fashion.
In view of this, Jpn. Pat. Appln. KOKAI Publication No. 11-97800 discloses a technique of the semiconductor laser module in which the lens position is fixed with a wedge-type spacer. This technique can fix the lens at an optimum position using the wedge-type spacer. In this technique, however, the lens is fixed at upper and lower positions thereof, and unlike in the present invention, the problem is posed that the optical elements cannot be optically connected easily with the best optical efficiency under various circumstances.
Thus, the conventional optical module apparatus harbors the problem that a plurality of boards holding a plurality of optical elements, respectively, cannot be easily connected optically with a suppressed loss by being physically connected and fixed.